The present invention arose out of an undesirable noise condition experienced with the drive of the auxiliary brush of the rotary brush sweeper described in U.S. Pat. No. 4,658,458 (the '458 patent), incorporated by reference herein. The sweeper of the '458 patent has a main rotary brush which rotates about a horizontally disposed axis and a rotatable auxiliary side brush which rotates about a generally vertical axis and is disposed to one side of the main rotary brush.
As an operator moves the sweeper about, on a floor or the like, the wheels of the sweeper rotate and this rotation is imparted to the auxiliary side brush. The auxiliary side brush is driven from one of the wheels of the sweeper which drives a drive pulley on the wheel to rotate a driven pulley on the auxiliary side brush. A friction belt joins the drive pulley to the driven pulley on the auxiliary side brush. The belt is conventional and typically fabricated of polyurethane, having a smooth, somewhat tacky, outer surface. The drive pulley is typically smooth surfaced and molded.
The auxiliary side brush is mounted on a pivotable support that holds the auxiliary brush in operative contact with the surface being swept and that permits the side brush to be selectively pivoted to an upraised position. In the upraised position, the actual distance between the drive pulley and the driven pulley of the brush is reduced. As a result, the drive belt of the auxiliary side brush is disengaged from the drive pulley which avoids undesirable rotation of an upraised auxiliary side brush.
A physical embodiment of a rotary brush sweeper that had been constructed in accordance with the teaching of the '458 patent was discovered to generate a persistent noise, squeal or screech when the auxiliary side brush is upraised and the now non-moving belt slides over the drive pulley which is still being rotated by the driven wheel.